The invention concerns a procedure for the control of a respirator device, in which one can set at least two different pressure levels of a breathable-gas supply and in which at least one respirator-treatment parameter is captured by a measurement technique and is evaluated for the purpose of controlling the respirator-treatment pressure.
In addition to the above, the Invention concerns an apparatus for monitoring at least one respirator-treatment parameter when a patient is supplied with the breathable gas. The apparatus features a sensor for capturing the time-wise evolution of the respirator-treatment parameter, the sensor being arranged in an air-delivery area which encompasses a respirator device as well as a connecting installation.
A not inconsiderable number of people suffer from sleep disturbances which affect the daytime well-being of these individuals and which [disturbances] may impair their social and professional capacity as well as quality of their life, to an occasionally considerable extent. One of these sleep disturbances is sleep apnea which is treated primarily with the so-called CPAP therapy (CPAP=Continuous Positive Airway Pressure). In this therapy an airstream consisting of a breathable gas is continuously supplied to the sleeping patient via a nose mask. By means of a hose the mask is connected to a respirator device which encompasses an aerator that produces a gas stream with a gauge pressure of 5 to 20 mbar.
The gas stream is supplied to the patient either under constant pressure or else—in order to facilitate the breathing work—at a lower pressure during the expiration stage. Even though sleep apneas occur only for short periods and make up a minor portion of sleep, in both cases the aerator operates during the entire sleep period (night), a fact which detracts from the acceptability of this sleep apnea treatment.
U.S. Pat. No. 5,245,995 teaches a CPAP respirator device which can be used on patients with sleep apnea. The breathable gas is supplied to the patient via a breathing mask, a source of compressed gas being provided in the area of the device. The source of compressed gas can be controlled as a function of airway resistance.
European Patent No. 0,373,585 describes a method for capturing the breathing resistance of a patient by means of ORM measurements. Here, the volumetric breathing stream is overlaid at a predetermined frequency with an oscillating volumetric stream featuring a low volumetric rise. Because of the periodic pressure variation occurring at the same frequency, one can generate a reading which is a function of the actual airway resistance.
From U.S. Pat. No. 5,318,038 one knows a respiratory measurement which involves the use of a pneumotachygraph in the gas delivery line. European Patent No. 0,705,615 describes a high-quality implementation of control for a respirator device based on the application of ORM measurements.
The procedures and apparatus in the prior art already provide greatly reliable means for preventing the occurrence of conditions threatening the patient's life. However so far it has not been possible to eliminate all impairments of the patient's quality of life. A special goal is to leave intact as much as possible the patient's own breathing activity, providing equipment-based support solely when the latter is indeed needed. This objective requires the optimization of the respirator device's control and regulation, as well as the use of appropriate regulating-technology components. In particular one must recognize at the earliest possible moment the occurrence of deviations from the patient's normal breathing activity, and react to them by means of the appropriate control and regulation of the respirator device.
Consequently it is the task of the present Invention to improve a procedure of the type described at the outset, in a manner such as to promote a prompt adjustment of the device's operation to the respective breathing condition.
This task is achieved by means of the Invention in that at least one respirator-treatment parameter is modified as a function of a pattern recognition. To carry out this pattern recognition, one captures—at least at intervals—the time-wise evolution of at least one respirator-treatment parameter and one analyzes it with respect to a typical individual pattern and/or with respect to an evolution pattern.
It is a further task of the present Invention to design an apparatus of the type described at the outset, in a manner such that, using a simple device structure, early changes in the respective respirator-treatment situation are recognized.
This task is achieved by the Invention in a manner such that the sensor is connected with an analyzer which carries out a pattern recognition, the analyzer being connected to a control installation for modifying at least one respirator-treatment parameter.
Carrying out a pattern recognition makes it possible to detect early changes in an existing breathing condition and thus permits a timely modification in the respirator device's controls. Here, advantage is taken of the fact that a plurality of respirator-treatment conditions are characterized by typical evolution patterns—for instance, of the respirator-treatment pressure or the respirator-treatment flow, or of variables proportional to them. In addition there is also the factor of the relatively early appearance, in the transition from one respirator-treatment condition to another, of typical evolution patterns.
The use of pattern recognition and the prompt introduction of modifications in the device's controls make it possible—even before a change in the respirator-treatment condition, noticeable by the patient, actually occurs—to counteract this change by adjusting the device's controls. The result is that, on one hand, no respirator-treatment conditions negatively affecting the patient's health are reached. On the other hand, the countermeasures are initiated at such an early point that relatively small changes in respirator-treatment parameters suffice to return to the desired normal condition. At the very least, the deviations from such normal conditions are kept within a narrow interval. The early triggering of the measures makes it possible to keep the intensity of those counteracting steps at a very low level which, as a rule, cannot even be noticed by the patient.
For greater ease of detection of significant patterns, it is proposed that the prevailing pressure level for breathing support be temporarily overlaid with a stimulating stream which oscillates at a specific frequency. In particular, this also comprises a change in the respective frequency during the application of the therapy.
A factor which contributes to the patient perception of the device's control setting as being pleasant is that—after the selective evaluation of an oscillatory pressure amplitude at the frequency of the stimulating stream, in the air supply to the patient (corresponding to a specific breathing resistance of the patient)—one carries out a selection of the respective pressure amplitude.
A typical application consists in the implementation of a CPAP respirator treatment.
A class of signals capable of evaluation is defined by the fact that at least one electric signal is evaluated during the pattern recognition.
Consideration is also given to evaluating a physical signal during the pattern recognition. The physical signal can be transformed into an electrical signal for further processing.
In order to support a systematic evaluation of the pattern recognition, it is proposed that in the context of the pattern recognition one carry out a derivation of error classes.
A typical signal evolution to be evaluated is defined in that an OPS signal is evaluated. By OPS signal we refer to an Oscillating Pressure Signal which corresponds to the numerical value of the impedance.
It is also possible that a pressure signal and/or a sound pressure and/or a pressure variation will be evaluated.
Because of the retro-acting effect, exerted by the production of a respirator treatment situation upon the electrical drive conditions of the compressed-air supply, consideration has also been given to evaluating an electrical drive parameter of the compressed-gas supply. This proves particularly practical if the regulation is carried out via an electric drive. Alternatively, however, the regulation can also be carried out independently of the pressure-building drive—e.g., via a valve.
In accordance with a typical evaluation run it is envisaged that, in the pattern recognition, it is distinctive form features that will be evaluated.
Consideration is also given to the possibility that, in the pattern recognition, distinctive time features and/or distinctive amplitude features will be evaluated.
The activation of predefined control runs, as a function of a pattern-recognition result, is promoted by the fact that an assignment to a class is carried out subsequent to the pattern recognition.
In order to increase the evaluation speed it is provided that the analyzer be coupled with a storage for supplying the comparative patterns.
Another contributory factor to a high processing speed is that the analyzer is coupled with a classifier.
A prompt evaluation of the time-wise evolution characteristics of the pattern that is to be evaluated is facilitated by the fact that the analyzer features a time-wise evolution analyzer and/or an amplitude-wise evolution analyzer.
A prompt evaluation of the form-wise evolution characteristics of the pattern that is to be evaluated is facilitated by the fact that the analyzer features a form-wise evolution analyzer.